On character hate, villains, and literary tropes

Just read a comment on my flist by copracat in which she made a fascinating point about character bashing in fanfic, which I wanted to expound upon.

It's a well-known phenomenon in fandom, that any character who comes between a pairing will be hated by some fans of that pairing. While it's not the only source of character hate, hatred of the interloper is perhaps the number one reason for char bashing. Sometimes the hated characters will simply be absent from fanfic, or otherwise ignored. But sometimes the chars will be bashed - portrayed in extremely negative, often wildly OOC ways, as scheming, selfish shrews out to ruin love affairs. When it comes to m/m pairings, such romantic interlopers are nearly always female characters (since almost all slashed male chars are canonically heterosexual, so their only canonical romantic partners are female. The reverse can be true with femme-slash pairings; Joxer was hated by some fans for being a potential threat to Xena/Gabrielle.)

copracat points out that such interlopers are a standard trope in romance fiction. ( How this carries over into fandom... )